1. Field of the Invention
The invention relates to a process for the preparation of organopolysiloxanes, modified with methacrylic esters, more particularly, this is accomplished by reacting -COH-group containing methacrylic esters with organopolysiloxanes, which contain SiX groups wherein X is alkoxyl, hydroxyl or chloro, optionally in the presence of catalysts.
2. Description of the Prior Art
Hardenable siloxanes with olefinic unsaturations are known and conventional in the art. These may be obtained by reacting a siloxane which has hydroxyl and/or alkoxy groups with a hydroxy ester of an olefinic, .alpha.,.beta. unsaturated carboxylic acid. In conjunction with polymerizable monomers, such siloxanes may be used as hardenable binders.
Products and processes for their preparation are described, for example, in the German Pat. Nos. 1,957,356, 1,957,357, and 1,957,358.
In German Pat. No. 1,957,356, for example, a paint binder is described which is based on a siloxane in combination with unsaturated monomers and which can be hardened by ionizing radiation. The binder consists of a film-forming solution of:
(a) 10 to 80, and preferably, 30 to 70 weight percent of vinyl monomers, and PA1 (b) 90 to 20, and preferably, 70 to 30 weight percent of a siloxane with olefinic unsaturation, which is obtained by reacting a siloxane, which contains 3 to 18, and preferably, 3 to 12 silicon atoms per molecule and has at least two functional groups, namely, hydroxyl groups and/or alkoxy groups with a hydroxy ester of an olefinic, .alpha.,.beta. unsaturated carboxylic acid.
The other German patents mentioned differ from the above essentially in the choice of unsaturated compounds which are capable of copolymerizing and are contained in the mixture in addition to the modified siloxane mixture.
As is evident from these patents, an electron beam with an average energy of 100,000 to 500,000 eV is required for curing this mixture of compounds. Such curing conditions can be fulfilled if the area where they are to be applied are favorably located. However, the scope of application of organopolysiloxanes, modified with methacrylic esters, for example, could be enlarged significantly, if it were possible to find organopolysiloxanes, modified with unsaturated compounds which cure under milder conditions and especially at a significantly increased rate. This is the basic object and purpose of the present invention.